The present invention relates to an acoustic diagnostic system and an associated method, which are particularly suitable for an automatic quality control of test objects, such as motors or ceramics.
Such a testing system and testing method are used, for instance, to detect and evaluate signals. Therein, a combination of measuring hardware and signal processing software is often used. This often requires the knowledge and experience of an expert, due to the complexity of such a measurement arrangement.
WO 98/01728 discloses a device to detect analog measurement signals to acoustically diagnose test objects. Vibration sensors are used to detect analog measurement signals from a test object. A computer is equipped with a standard interface card to digitize the measurement signals. A switching signal generates a trigger signal, which can be input via an interface. This interface is preferably a serial interface. Via the trigger signal, a control program in the computer switches the input of the measurement signals on and off.
It is one object of the invention to provide an acoustic diagnostic system and an associated method, which enables automatic quality control in a simple manner.
According to one formulation of the invention, this and other objects of the invention are achieved an acoustic diagnostic system, which includes a sensor mechanism to convert mechanical vibrations into electrical signals. The acoustic diagnostic system furthermore includes a signal conditioning unit to amplify and low-pass filter the electrical signals and an analog/digital converter to convert the amplified and low-pass filtered signals into discrete digital data. In addition, a signal processing unit for signal analysis, for extraction of characteristics, and for classification of error classes and/or quality classes, which are associated with a respective test object is provided. Finally, the acoustic diagnostic system includes an archive to automatically archive an occurrence and a frequency of the error classes and/or the quality classes.
According to another formulation of the invention, this and other objects are achieved by a method to control the quality of a test object, which includes the steps of converting mechanical vibrations into electrical signals; amplifying and low-pass filtering the electrical signals; converting the amplified and low-pass filtered signals into discrete digital data; analyzing the signals; extracting characteristics; classifying error classes and/or quality classes, which are associated with the respective test object; and automatically archiving the occurrence and the frequency of the error classes and/or the quality classes.
Due to the acoustic diagnosis, the diagnostic system enables an automatic and straight-forward, verifiable quality control, in particular in the manufacturing process of products, for which an acoustic diagnosis permits conclusions as to the quality of the products.
Contrary to previous acoustic tests, which must often be performed by specialists, the diagnostic system according to the invention can be used as often as desired. Additionally, the automatic archiving of the quality tests allows for reliable and straight-forward, verifiable reexamination at any time.
The integration of the diagnostic system into a production process is performed in that the diagnostic system includes a controller, or in that it is connected to a controller, which control of the production process of test objects.
A descriptive classification of test objects is ensured in one of two ways. As a first alternative, the diagnostic system includes a component, which, based on an input signal, determines several classifications. As a second alternative, the diagnostic system includes a component, which based on an input signal that is assigned to the test object, determines several characteristics for the classification of the test object. Therein, the characteristics or features assigned to each class are color-coded.
An optimized determination of the number of features is ensured in that the diagnostic system includes a component to determine redundant features, which, in turn, determine a correlation of existing features.
A capability to filter redundant features is provided by means of the diagnostic system for creating a correlation matrix to visualize redundant features.
Advantageous applications of the diagnostic system are found in quality control, in particular in the quality control of self-energized test objects, such as motors, and/or in the quality control of separately energized test objects, such as glass or ceramics.